WHAT do you get when you cross a tomato with a snapdragon? A cancer-fighting fruit, according to scientists.

Large-scale production of the genetically modified purple tomatoes is under way in Canada, where the first 1200 litres of purple tomato juice is ready for shipping, the BBC reports.

Developed in Britain, the dark pigment - known as anthocyanin - aims to give the tomatoes the same potential health benefits as antioxidant-rich blueberries. Studies on animals show the pigment could help fight cancer.

The tomatoes were developed at the John Innes Centre in Norwich, England, where Professor Cathie Martin hopes the first delivery of large quantities of juice will allow researchers to investigate its potential. In time, they hope to see the nutritional value boosted of other everyday items, such as tomato sauce.

"With these purple tomatoes you can get the same compounds that are present in blueberries and cranberries that give them their health benefits - but you can apply them to foods that people actually eat in significant amounts and are reasonably affordable," she said.

I hope this will serve as a vanguard product where people can have access to something that is GM but has benefits for them."

Restrictions on genetic modification in the European Union led Professor Martin to look to Canada to develop the technology.

The purple pigment is the result of the transfer of a gene from a snapdragon plant, which allows the anthocyanin to develop.

"It is frustrating that we've had to go to Canada to do a lot of the growing and the processing and I hope this will serve as a vanguard product where people can have access to something that is GM but has benefits for them."

Because all the seeds have been removed from the initial shipment of juice coming to Norwich, there is no genetic material to risk any contamination.